Research On Key Generation From OFDM Subcarriers

Secret key generation exploiting wireless channel characteristics is one research aspect of physical layer security,and it is a new way to guarantee security of wireless networks.Besides,the OFDM subcarriers are advantage for key generation.This paper investigated secret key generation schemes from key extraction and key agreement,achieving some innovative contributions as following:First,traditional key extraction from OFDM subcarriers has the problem of low utilization rate.A new key extraction scheme using oblique sampling has been presented.This scheme taking advantage of the characteristics of subcarriers' random distribution,slantly sampling in bit matrix,which improves the utilization rate of channel information.Simulation results show that the proposed scheme can achieve higher key generation rate compared with the traditional secret key extraction mechanism in OFDM system on IEEE 802.11 a standards.And then,traditional key extraction from OFDM subcarriers has the problem that the generated key is lack of randomness.This paper proposes to introduce random perturbation,an operation which based on the principle of stream chip.This scheme using random sequence xor the related bits in bit matrix improves the randomness of the total key.Simulation results show that the generated key passes more NIST tests compared with the key extraction without random perturbation.That show the fact that generated key is of more randomness.Finally,for the key agreement,how to find an algorithm with higher speed and more applicability is a very important problem.Therefore,this paper proposes a flexible and efficient scheme.In the scheme,it is based on error correcting codes and sub key agreement.The traditional key agreement is based on total key,which wastes the channel information when key reconciles fails.This scheme is based on sub keys,which can save most agreed sub keys when agree fails.In terrible channel condition,compared with traditional,this algorithm is more efficient.And this method is available for Low Density Parity Check Code(LDPC)and Hamming Code.Simulation results show that efficiency can be increased by 50% when the original key disagreement rate is 10%,and the Hamming code and the LDPC code can successfully agree the keys.